In the evolution of computer systems, highly centralized mainframe computers initially dominated the industry. Gradually, less expensive and more versatile minicomputers were developed. With the advent of personal computers, computing power was distributed to end users at the desktop. Eventually, several personal computers were coupled together to form a network. A computer network allowed end users to share files, applications, and peripheral hardware (e.g. printers, storage devices such as disk drives, etc.). Thereby, individuals and work groups could share information and expensive computing resources, while increasing the reliability of the computer system. This type of arrangement came to be known as Local Area Networks (LANs).
Basically, a LAN is comprised of a number of data terminals or data terminal equipment (DTE) which are coupled to transmission lines (i.e. circuits, channels, or trunks) through transceivers. A DTE is an individual device such as a personal computer, a workstation, a mainframe computer, a dumb or intelligent terminal, etc. A transceiver couples a DTE to a transmission line and performs any necessary signal conversions. The transmission lines conduct bits of data between the interconnected DTEs.
The DTEs could be coupled together in various network configurations (i.e., topologies). Some of the more popular topologies include the star, ring, tree, and bus topologies. In addition, different types of protocols for these networks also evolved. A protocol defines the format and relative timing of message exchanges in the LAN. One widely used protocol is known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD), which is also referred to as Ethernet. The Institute of Electrical and Electronic Engineers (IEEE) standard 802.3 sets forth the specification for Ethernet. According to IEEE 802.3, the transmission lines coupling the various DTEs on an Ethernet LAN can be one of several different physical media. Some examples of different media which can be used include twisted pairs, Attachment Unit Interface (AUI) cables, coaxial cables, and fiber-optic cables.
Traditionally, electrical and electronic communications were implemented by twisting together two insulated copper wires; hence, the term twisted pair. To this date, many telephone systems are still based on the twisted pair, and the wiring within buildings for telephone systems is commonly comprised of pairs of copper wires. Consequently, computers on a network can be conveniently coupled together via the twisted pair wiring already existing in most workplaces. However, one disadvantage associated with twisted pairs is that the electrical characteristics of unequalized and unconditioned copper wire introduce distortions which increase with speed and distance.
AUI cabling, is comprised of four twisted shielded pairs for conducting differential signals, a 12 volt power line, and a master shielding which encompasses all the wires. The effective distance for AUI cabling is approximately 50 meters.
For broadband systems and for many baseband systems, an alternative to twisted pairs is coaxial cable. Coaxial cables have a single center conductor, surrounded by an insulator which is, in turn, surrounded by a metal shield (e.g., wire-mesh, foil, etc.). Coaxial cables can handle greater bandwidths and are less susceptible to outside noise. However, coaxial cable is typically more expensive.
Presently, fiber optic cables are being implemented in computer networks. Fiber optics is not susceptible to electrical noise and has a very high bandwidth and transmission speed. However, splicing and tapping the optical cable is an expensive and difficult process. Thus, each of the different media has its advantages and drawbacks. There is no one "best" transmission medium. The selection of a medium depends on the use to which it will be put.
In order to increase flexibility and versatility, computers are being designed so as to be compatible with different transmission media which can be found in a network environment. The goal is to provide the computer with the capability of interfacing with the medium ultimately selected by the end user. Typical prior art approaches provided multiple input/output (I/O) ports. Each port is matched to interface with one of the various transmission media. In order to select the proper port corresponding to the chosen media, jumpers are provided on the printed circuit boards within the computers. A jumper is inserted onto the printed circuit board to provide a signal path for enabling the desired port. The other ports are disabled by removing their jumpers. One disadvantage with this approach was that inserting and removing the jumpers was quite cumbersome, tedious, time consuming, and rather annoying. A more sophisticated approach entailed substituting switches in place of the jumpers. Ports were enabled and disabled by means of the switches, thereby eliminating the hassle of inserting and removing jumpers.
However, both prior art approaches (i.e., jumpers and switches) suffered several disadvantages. In order to effectuate the changes via the jumpers or switches, the computer is first powered down, the computer housing is then removed, the printed circuit board containing the jumpers or switches is unplugged from the motherboard, the proper jumper insertion/removal or switching is made, and then the board is inserted back into the motherboard and the computer housing is replaced. Clearly, this is a cumbersome, labor intensive and time consuming task. Another disadvantage is that the user might accidentally cause physical damage to some part of the computer while trying to effectuate the jumping/switching. Yet another disadvantage is that the user might not know how to effectuate the changes. More likely, a user would not know which of the jumpers/switches corresponds to which of the multiple ports. In the case of switches, the user might not know which state results in a short circuit and which state results in an open circuit. Most users would require detailed instructions and documentation. Even then, inadvertent errors are easily made. In which case, the user has to repeat the whole process all over again. Furthermore, the jumpers and switches increase production costs in terms of additional parts, increased manufacturing times, testing, etc.
Thus, what is needed is an apparatus and method which permits the user to set-up or change the transmission media type for a computer on a local area network quickly, easily, and safely. It would also be preferable if minimal additional hardware other than those already available in computer systems designed for a networking environment were required for such an implementation.